Volitional attention is a complex neuropsychological process that can involve aspects of vigilance and monitoring, cognitive control and dynamic interactions between attention and other psychological domains, such as working memory and contextual processing. This complexity of attentional processing is best typified by the so-called AX-continuous performance task in which subjects must not only detect a particular item ('X') from a rapid visual serial presentation but also gate the motor response to that stimulus based upon the incidence of previous serial items (task rule: respond to item X when it is preceded by item A but not item B). The relevance of this kind of task is revealed by its diagnostic specificity: patients with schizophrenia or attention deficit disorder (which both include attentional impairments) each show specific and dissociable patterns of errors on the task. Despite the usefulness of this task, it has yet to be successfully implemented in animal models. The purpose of this task is to develop an analog of the AX-continuous performance task that can be used to study attention, cognitive control and working memory in non-human primates. We will develop, program and implement a touch screen apparatus for the evaluation of performance of such a task by Vervet monkeys. The development of such an approach to modeling contextual aspects of attention, in particular, in animals should be a major advance linking pre-clinical psychopharmacological studies and treatment-based research for schizophrenia. [unreadable] [unreadable]